[Boater Sam]

The mains voltage dropped to a more sensible 243 volts this evening, the milking machines are on. With the AVO 8, voltages are now more in line with the sheet.

Tried shunting the IF to ground after the detector diode, no joy, and on the volume control, same racket.
Disconnected both top cut tone caps, no joy, still howling.

Sat and thought about it, decided to see if I could get a clean audio output both on the EL41 grid and on the triode grid. On gram its clean, on any waveband putting a signal into the EL41 it is still obvious that there is oscillation as well. The EL41 has a 47k grid stopper already.

Considered that it had to be before the volume control, as I said before pulling the IF valve V2 killed it.
Looking at the circuit I notice that there is no grid stopper on the g1 of the IF amp. I wonder if.........

Cut the wire from the IF transformer to g1, insert 8k2 resistor, success! No howling, clean reception on all bands. Tried smaller values, but it seems to need 8k2.
Removed all other extra components including the extra screen feed components for V2 and it is still working fine.

Now I don't really want to redesign the set but unless anyone can tell me what else I could do, its staying like this.

Comments most welcome please.